The Seahawks also are considering placing cornerback Brandon Browner on injured reserve because of his groin injury, league sources told ESPN NFL Insider Adam Schefter. Browner was not expected to be available until mid-December, coach Pete Carroll said last week.

Browner also is facing a one-year suspension from the NFL for violating its substance-abuse policy, league sources have told ESPN. Browner, who has already had his appeal hearing on the matter, missed the final four games of last season for violating the league's PED policy.

San Francisco released Cox (5-foot-11, 189 pounds) this month. The 26-year-old corner had two tackles in nine games for the 49ers this season. He started nine games for the Denver Broncos in 2010 but sat out the 2011 season after he was accused of sexually assaulting a woman at his apartment in September 2010. He was acquitted of the charges in 2012 and signed with San Francisco later that year.

Thurmond will be eligible to return to the active roster Dec. 23, before the final game of the regular season.

A member of one of the NFL's top secondaries, Thurmond has one interception and one sack thus far. His pick came in the team's last game, against Minnesota, and he returned it 29 yards for a touchdown.

If Browner is placed on injured reserve or suspended, the Seahawks might already have a player in mind to fill the void.

On Monday, Carroll said it's possible the Seahawks will try to re-sign veteran cornerback Antoine Winfield, a three-time Pro Bowl player with the Vikings who signed with Seattle as a free agent in April but retired before the season began when it appeared the team was set to go with younger players in the secondary.

"He's a really good football player," Carroll said Monday morning on 710 ESPN Radio in Seattle. "With the needs that we may have going into this game, that's a possibility. We'll figure that out when the time comes. But he's a really quality guy to bring into your team at a time like this. He's knows his way around, and everybody respects the heck out of him."

The 36-year-old Winfield is considered an excellent cover corner. He started 16 games for the Vikings last season, finishing with three interceptions and 13 passes defensed.

The Seahawks (10-1) own the league's best record and will host Drew Brees and the high-powered New Orleans Saints (9-2) on Monday night in a matchup of the NFC's top teams.

ESPN.com Seahawks reporter Terry Blount and information from The Associated Press contributed to this report.